1. Field Of The Invention
The method of the present invention relates to the drilling of radial hydrocarbon and environmental wells, with offset well bores from vertical, directional or horizontal orientation. More particularly, the present invention relates to a drill string carried within a carrier string, and the method of orienting the two strings while both strings are downhole so that the strings are oriented in the same direction for drilling multiple radial offset well bores without retrieving either string from the hole.
2. General Background
In the field of drilling for gas, oil, or other hydrocarbons, as well as environmental wells, the drilling of radial wells is known in the art. For example, when a rather large pocket of oil or gas is hit in a field, oftentimes, numerous radial well bores, which are wells drilled radially off of a vertical, horizontal, or directional hole, are drilled to maximize the recovery of the liquid or gaseous hydrocarbons from the site. Such drilling is undertaken with the use of a steerable motor assembly consisting of a mud motor assembly of several types, including an articulated motor, double bent housing, singular bent housing, or bent sub with motor, which would be attached to the bit. The type of mud motor and bent housing utilized will determine the angular configuration of the radial well.
In accomplishing this method, a first straight, directional, or horizontal hole is drilled using conventional techniques. After completion of drilling, the drill string is retrieved from the well bore, and the radial drilling process is now ready to be implemented utilizing a two-string drilling technique. The first drill string is assembled with an upstock (which is a type of whipstock) which is multi-orientable without retrieving from the well bore. This string would now be called the carrier string, since it has the ability to carry another drill string inside of the carrier string. The carrier string is now lowered into the well bore to the site of the radial well bore point of origin. The upstock has an opening in its sidewall, to help guide yet a second, inner drill string therethrough, and begin its radial well bore. However, there are tremendous shortcomings to the present state of the art. The most prevalent is the need to be able to simultaneously orient both the outer and the inner drill strings so that the opening of the upstock ramp and the bent housing motor assembly are aligned. Additionally, the two strings must be oriented in the proper direction.
In the present state of the art, in order to accomplish this, the well is drilled, the first string is retrieved, and a carrier string with a upstock is lowered into position in the original wellbore. The inner string, with the bent housing motor assembly is then lowered into the carrier string, and the drilling process is ready to begin, as this assembly exits off of the upstock ramp and drills the first radial. Usually there are multiple radial wells to be drilled from this first hole. Therefore, after drilling the first radial, the inner string is pulled out of the hole, the upstock is retrieved, reset, and relowered back into the hole for the second radial. Each subsequent radial is drilled in this manner. Since time is money in drilling oil or gas wells, the time expended in this process is very extensive and the cost is very high.
These time and high cost factors become critical in certain settings. For example, it has been determined that the oil and gas reservoirs which have been abandoned in the United States may contain some 330 billion barrels of hydrocarbons, and some fields leaving some 70% of the hydrocarbons underground due to the poor recovery ability of correct production techniques. Therefore, if greater amounts of oil are to be retrieved in such settings, radial wells are very important to maximize recovery. However, as explained heretofore, the expense and time is almost prohibitive, under the current technology of drilling radial wells.
Therefore, it is critical that there be in the art a method of drilling multiple radial oil, gas, or environmental wells, which cut the time drastically and therefore reduce significantly the cost of drilling such multiple wells from a single first vertical, directional or horizontal well.
In the current state of the art there are numerous patents which address the drilling of radial wells, and these are cited in the Prior Art Statement which will be submitted in the filing of this application.
Other objects of the invention will be obvious to those skilled in the art from the following description of the invention.